The aim of this proposal is to study further the mechanisms of impulse origin in carotid body chemoreceptors. Good progress has been made, but, the precise role of carotid body cells and nerve endings has to be determined. To accomplish this the following studies are proposed: 1) Further analysis of the role of temperature and osmolarity on cells and nerve fiber discharges since it has become clear that these receptors have functions other than those involved in regulating respiration and blood pressure; 2) Quantitative analysis of the effects of dopamine and ACh (putative transmitters contained in glomus cells) on the mass receptor potential of nerve endings and the influence of different ions on these processes; 3) Whether or not ACH and dopamine are contained in the same or different cells; 4) Metabolization of desoxyglucose during rest and activity to see which elements (cells, nerve endings or fibers) participate in activation; 5) Slices (20 microns) of carotid body tissue will be used to study the functional relationships between cells and nerve endings under direct visual observation with Nomarski optics; 6) Tissue and/or organ culture to grow glomus cells and sensory or sympathetic ganglia will be employed to determine the sensitivity of growing nerve fibers to chemical or natural stimuli before and after apposition to the cells; 7) The intracellular pH and ionic mobilities in glomus cells will be studied to learn about mechanisms of glomus cell activity. These studies involve the use of intracellular recordings registering from nerve fibers, fluorescence microscopy and autoradiography.